Both lymphoid and tumor cell lines have been established from patients with malignancies. Cell products monitored included melanin, immunoglobulin, carcinoembryonic agents, hormones and hormone receptors. Characterization of all the cell lines included cytogenetic analysis, growth in immunosuppressed mice, cytotoxicity assays, estrogen and progesterone receptor proteins, mycoplasma, morphology including ultramorphology, growth patterns, media requirements and allelic isozyme profiles. Studies were made of glycoproteins in spent media and cell extracts that were stimulatory or inhibitory to phytohemagglutinin-stimulated peripheral blood lymphocytes. A survey of the presence of double minute chromosomes (DM) and homogeneous staining regions (HSR) of chromosomes in the cell lines and in fresh cells was carried out. Hormone receptors were detected in non-endocrine malignancies.